1. Field of the Invention
This invention relates to a diagnostic apparatus for identifying faults occurring in an electronic control system of the type used for controlling electrical devices within an automobile. While the present invention is described with relation to the control of accessories within the vehicle, the system and method could also be used for controlling any subsystem of the vehicle that is electronically controlled, such as the ignition system, the transmission shifting mechanism, electronically controlled braking systems and traction control systems, power windows, etc.
2. Description of the Prior Art
A typical prior art solution to the problem of verifying the integrity and performance of an electrical accessory system is illustrated in U.S. Pat. No. 4,924,398 as including a separate testing unit that is removably coupled through a connector into the electrical system of the vehicle. The external testing system is utilized to interrogate and sense the proper operation of various electrical accessories.
Another prior art solution is disclosed in U.S. Pat. No. 4,908,792 wherein a separate ROM memory is provided for stimulating a microcontroller with a separate test program to exercise and sense the proper operation of the electrical system. This solution fails to test the operation of the microcontroller in conjunction with its originally programmed code.
In contrast to the prior art solutions, the present invention utilizes existing sensors, indicators/actuators, power drivers and microcontroller by enabling additional software in the microcontroller that will sense the signal from the actuated sensor and responsive thereto actuate an audible indicator for signalling that the sensor, the interconnect wiring to the controller and the microcontroller portion of the system are operating properly. The microcontroller will also sense a signal from each of the power drivers indicating that the power driver has received the control actuation signal from the microcontroller and responsive thereto has successfully changed the conductive state to apply or remove power coupled to the load. A visual indicator will be actuated indicating that the power driver has responded to the signal, with the visual signal being deactivated within approximately one second unless the power driver indicates that an open circuit or a shorted circuit is being sensed.
It is therefore a first object of the present invention to utilize existing sensors, wiring and microcontrollers, power drivers, actuators, and indicators within the automotive electrical system for indicating the proper operation of the subsystems, without resort to additional equipment that must be coupled to the vehicle system through wiring and connectors. It is also an object of the present invention to indicate that the sensor, interconnecting wiring and the microcontroller sections of the system are operating properly, as well as providing a separate indication that the microcontroller and power driver sections of the accessory system are operating properly.